Thousands of migrants who had been stuck for days in southeastern Europe started arriving in Austria early Saturday after Hungary escorted them to the border.

Austrian police reported 6,700 new arrivals from Hungary since midnight. Spokesman Helmut Marban said that about 4,200 people crossed the border at Heiligenkreuz, near the southern city of Graz, while the rest used the Nickelsdorf crossing near Vienna.

Police said border controls continue to be in place, with vehicles being selectively checked and those inside asked for valid travel documents.

The development comes after thousands of migrants, many lacking food and water, were trapped in southeast Europe, in some cases for several days, after countries began putting up barriers that blocked their passage to Western Europe.

The migrant path was first blocked by Hungary, which sealed off its southern border with Serbia with a razor-wire fence and tough other tough measures to keep people out.

That caused a massive influx of more than 15,000 people over three days into Croatia, which could not cope and then began escorting people to the border with Hungary.

In response, Hungary transported the migrants to the border with Austria by bus and train.

Meanwhile, Slovenia has blocked off its borders and used pepper spray on migrants late Friday.

Some, however, made it in earlier and hundreds of people camped out overnight in Obrezje, a town in Slovenia just across the border from Croatia. Authorities only allowed limited numbers of families with women and children to continue on. Many migrants put up tents while others tried their best to keep warm as the temperatures dipped overnight.